Overwing emergency exit systems on existing commercial aircraft normally use a plug-type hatch requiring the operation of a single handle to unlatch the hatch. The hatch must then be manually lifted out of its location in the body structure and either placed inside the aircraft or thrown out through the body opening.
Automatically powered systems for opening doors to the exterior of aircraft are known in the art. However, such systems are not generally applicable to overwing emergency exit hatches because their powering and linkage mechanisms can intrude into the passenger headroom area or overhead bin storage area. In an overwing emergency exit door application, the powering and linkage mechanisms must substantially fit within the envelope between the outer skin of the aircraft and the interior cabin liner or storage bins. Additionally, the powering and linkage mechanisms should be configured to allow a standard-sized window to be placed in the central region of the door, since uniformity of appearance is greatly desired by aircraft customers.
An automatically powered outwardly opening emergency exit door is described in U.S. Pat. No. 5,031,863. The '863 device includes a door frame and a pair of hinge arms for providing swinging movement of the door between open and closed positions relative to an overwing aircraft fuselage opening. The door may be moved by initiation of either an interior handle or an exterior handle. Either component is mechanically linked to mechanisms that release the door and allow it to swing open. Various pins and channels are provided to help guide the movement of the door in a manner that causes the door lower edge to initially move upward and inward before moving outward. Once the door lower edge is cleared of the opening and stop pads have cleared their respective stop pads, actuators rotate both the hinge arms and the door outward. The operation of the '863 device is satisfactory, however, it is the opinion of the present inventors that a more intuitive approach may be to use a door assembly having a lower edge that initially moves downward and outward.
As a result, there exists a need for an overwing emergency exit door assembly that automatically opens after being unlatched and has a door motion that moves downward and outward. The ideal door assembly should not violate passenger headroom or overhead storage bin area, and should optimally allow the installation of a standard-sized window. In addition, it is important to arrange the door components such that only a relatively small amount of effort is required to quickly open the door to a canopy position for emergency evacuations. The present invention is directed to fulfilling this need.